Testosterone 5.alpha.-reductase is an enzyme that reduces testosterone, a male hormone (androgen), into dihydrotestosterone. The produced dihydrotestosterone has been elucidated to play an important role in the mechanism of the generation and progress of prostatic hypertrophy, male pattern alopecia, and acne (acne, pimples, etc.) (J. Steroid Biochemistry, 11, 609 (1979); J. Clinical Endocrinol and Metabolism, 56, 139 (1983); and Japanese Patent Application Laid-Open (kokai) No. 1-139558). Indoles are known as compounds that exhibit testosterone 5.alpha.-reductase inhibitory activities, (Japanese Patent Application Laid-Open (kokai) No. 4-244061, WO 93/02050).
.alpha.-Adrenergic receptors are known to participate in contraction of smooth muscles. Particularly, recent research has revealed that .alpha..sub.1 -adrenergic receptors strongly participate in contraction of the sphincter in the human bladder neck (J. Urol., 134, 396 (1985)). Therefore, blockers of the receptors are considered to serve as drugs that are capable of selectively treating urination disorders and frequent urination accompanied by prostatic hypertrophy. As compounds that have a blocking action against such .alpha..sub.1 -adrenergic receptors, there are known piperazine derivatives (WO89/12634, WO90/03972).
Disurea, which aged people frequently suffer, is caused by constriction of urethra due to the tonus of sympathetic nerves present in the bladder neck or by urinary obstruction associated with prostatic hypertrophy, and makes urination difficult. In recent years, disurea has been treated by the combined use of an .alpha..sub.1 -adrenergic receptor blocking agent and an anti androgenic agent. However, this is not satisfactory in view of the drug administration schedule.
Therefore, it is desired to develop drugs having both benefits of symptomatic therapy, which exerts immediate effects as exerted by .alpha..sub.1 -adrenergic receptors, and of radical therapy, which exhibits its effect slowly but radically, as in the case of testosterone 5a-reductase inhibitors.
Although International Patent Publication No. WO 95/26955 discloses indole derivatives that have both an .alpha..sub.1 -adrenergic receptor blocking action and a testosterone 5.alpha.-reductase inhibiting action in combination, further enhancement of the effects and activity thereof must be attained.